1. FIELD OF THE INVENTION
The invention relates to a holding device for wafer-like objects, in particular, semiconductor wafers, having a frame at least partially surrounding the wafer without contact and holding elements originating from the frame and acting on the wafer. The invention also relates to a method of treating semiconductor wafers in which the wafers pass through at least one process step or a sequence of process steps comprising one or more transport operations.
2. RELATED ART
In the production on of semiconductor wafers as starting materials for electronic components or solar cells, the wafers are subjected to a series of process steps during, before and/or after which the wafers are transported. In particular, the wafers are subject to inspection operations in which the wafer surfaces are examined for properties such as, for example, geometrical perfection, particle freedom or chemical purity, and identification operations in which the wafers are provided, for example, with markings or inscriptions before they are delivered to the final packaging and are made ready for shipment.
Hitherto, special gripping devices such as, for instance, vacuum pickups or gripping tongs having a frame partially surrounding the wafers without contact and manually operated holding elements acting on the outside circumference of the wafers have been employed for holding and transporting wafers in such operations.
Vacuum pickup, like wafer transport, by means of transport bells, has the disadvantage that even gentle contact with the wafer surface leads to defects. The defects can be rendered visible, for example, with the aid of particle measurements or particular etching solutions. The pattern reveals the track of the transport belt or the vacuum pickup on the wafer surface. Although known gripping tongs avoid this disadvantage, they are difficult to operate as they must be precisely positioned for gripping, which is not feasible in the long term. In addition, the gripping tongs are unwieldly and like vacuum pickups, are suitable only for localized use. The known gripping tongs are not suitable for more extensive transport paths, so the wafers have to be picked up at different points of treatment and have to be passed on. In each of these gripping operations, there is the risk of damage to the sensitive wafers.
The object of the invention is to provide a holding device which makes possible the gentle, simple and reliable pick-up and release of wafer-like objects in particular, semiconductor wafers, and makes it possible to reduce the number of gripping operations necessary.